Hot Corrosion of a Single Crystal Ni-Base Superalloy by Na-Salts at 900°C

The hot corrosion behaviors of a single crystal (SC) Ni-base superalloy coated with Na2SO4 and 75 wt.% Na2SO4-25 wt.% NaCl mixture were studied in air at 900°C. The results showed that the corrosion productions were laminar structure, porous and easily spalled. And sulfides formed quickly in the deep SC superalloy under the corrosion production. The addition of NaCl into Na2SO4 considerably accelerated the corrosion of the SC superalloy, and the corrosion scale became more porous. The hot corrosion process was explained based on sulfide formation and its subsequent oxidation.